The viability of isolated rabbit nasal mucosa in the Ussing chamber, and the permeability of insulin across the membrane

The viability of isolated rabbit nasal mucosa (lateral wall) and the permeability of insulin across the membrane have been tested in an Ussing chamber. The short-circuit current (I_sc) was relatively stable between 1 and 10 h. Average I_sc for this period (I_sc,1-10) was 92 ± 13 μA/cm². The viability of the tissue was longer than 10-12 h, where I_sc was about 85 and 66% of I_sc,1-10, respectively. During 1-10 h the average potential difference (PD) was 6.4 ± 1.5 mV (mucosal side was negative) and the average tissue resistance (TR) was 69 ± 8 Ω cm². The appearance of insulin at the serosal side is expressed as ‰ of the initial insulin concentration (8 mg/ml) at the mucosal side. Mean appearance rate was 0.44 ± 0.34‰ h^-1, equivalent to an apparent penetration coefficient (P_app) of 0.24 × 10^-6 cm/s. The same value, corrected for possible degradation and/or adsorption at the serosal side, is 0.73 ± 0.42‰ h^-1 (P_app = 0.4 × 10^-6 cm/s). The concentration of insulin at the mucosal side between 5 and 90 min was relatively constant, the average recovery being about 85%. The method is found to be useful for physiological and toxicological studies. Whether it is useful to screen absorption enhancers for peptides remains to be confirmed.